The present invention relates to a unit for applying adhesive labels to a continuous strip.
More particularly, the present invention finds use in cigarette packers and discloses a unit for the application of adhesive labels, spaced part at a predetermined pitch, to a continuous strip of wrapping material that will be divided ultimately into single leaves suitable for enveloping groups of cigarettes.
By way of example, U.S. Pat. No. 4,300,676 discloses a packet of cigarettes having an inner wrapper of metal foil paper furnished with an adhesive label, which the user removes to gain access to the cigarettes.
Adhesive labels are fed to the cigarette packer generally on a backing strip of silicone-coated material, decoiling from a roll; the labels are stuck to this same strip in a substantially continuous succession. The cigarette packer comprises a detach and transfer station at which the silicone-coated backing strip is routed over the sharp edge of a diverter element, thus causing the single labels to separate by degrees from the backing strip.
The adhesive labels, positioned with the adhesive face directed toward the strip of wrapping material, are induced to stick to the surface of this same material by a jet of pressurized air released intermittently from a nozzle located downstream of the aforementioned diverter element.
One drawback encountered with this solution is that it betrays a total lack of precision in positioning of the label on the continuous strip, given that when in flight, during the transfer step, the label is not fully under control when exposed to the force of the air jet and in effect remains completely free of any restraint.
A second type of unit for applying adhesive labels to a continuous strip of wrapping material functions by directing the silicone-coated backing strip over a diverter element positioned facing the continuous strip to which the label will be applied.
The label detached from the backing strip comes to rest on the continuous strip of wrapping material, advancing beneath the diverter element; a pressure roller located downstream of the diverter element then pinches the label against the continuous strip, causing it to stick progressively to the wrapping material. In both cases, the silicone-coated backing strip is fed toward the diverter element intermittently.
Bearing in mind that the labels are spaced apart on the backing strip by a distance less than the distance at which they will be applied to the strip of wrapping material (one label per single wrapper), the linear velocity at which the strip of wrapping material advances, and therefore the tangential velocity of the pressure roller, will be greater than that of the backing strip.
Consequently, the adhesive label detached from the silicone-coated backing strip is subjected by the pressure roller to a tensioning action that can cause it to be torn or otherwise damaged.
Accordingly, the object of the present invention is to provide a unit for applying adhesive labels to a continuous strip, such as will be unaffected by the drawbacks mentioned above and capable of high speed operation.